New molten salt chemistry allows solar thermal energy to drive calcium oxide production without any carbon dioxide emission. This is accomplished in a one pot synthesis, and at lower projected cost than the existing cement industry process, which after power production, is the largest contributor to anthropogenic greenhouse gas emissions.

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Zinc-air batteries have been proposed for EV applications and large-scale electricity storage such as wind and solar power. Although zinc-air chemistries batteries are very promising, there are numerous technological barriers to overcome. We demonstrate for the first time, a new rechargeable zinc-air battery that utilizes a molten Li 0.87 Na 0.63 K 0.50 CO 3 eutectic electrolyte with added NaOH. Cyclic voltammetry reveals that a reversible deposition/dissolution of zinc occurs in the molten Li 0.87 Na 0.63 K 0.50 CO 3 eutectic. At 550 °C, this zinc-air battery performs with a coulombic efficiency of 96.9% over 110 cycles, having an average charging potential of ~1.43V and discharge potential of ~1.04V. The zinc-air battery uses cost effective steel and nickel electrodes without the need for any precious metal catalysts. Moreover, the molten salt electrolyte offers advantages over aqueous electrolytes, avoiding the common aqueous alkaline electrolyte issues of hydrogen evolution, Zn dendrite formation, "drying out", and carbonate precipitation.

A straightforward synthetic route to nano-VB 2 particles, via planetary ball milling of elemental vanadium and boride in a 1:2 equivalent ratio is presented. Variation of the mechanochemical synthesis milling speed and milling time is used to optimize this nano-VB 2 for use as a high capacity anode material with enhanced charge transfer and increase voltage. VB 2 releases, via electrochemical oxidation, an unusual 11 electrons per molecule at a favorable, highly level electrochemical potential. Coupled with an air cathode, this anode with volumetric and gravimetric capacity of 20.7 kAh/L and 4.1 kAh/kg, has energy density greater than that of gasoline.Higher energy density batteries are needed for applications ranging from consumer electronics, industrial, medical, military applications, to hybrid and electric vehicles. The quest for a long, uninterrupted power supply has focused on lithium-ion batteries for a number of years, but recently an alternative material, vanadium diboride (VB 2 ) has been introduced as a potential high capacity anode, with a VB 2 air battery (utilizing an air-O 2 cathode) shown to have an order of magnitude higher capacity than lithium-ion batteries. 1 In an unusual multiple electron process, each VB 2 releases up to eleven electrons at a level discharge potential, which does not exhibit separate voltage plateaus. While electrochemically recharging this eleven electron anode is challenging, 2 the system has been demonstrated to be chemically rechargeable. 1 Using the VB 2 air battery has a theoretical discharge potential of 1.55 V, as calculated 3 from the thermodynamic free energy of the cell reactants and products: 4,5 Anode :Cell :With a density of 5.10 kg/l, the 11 electron per molecule VB 2 oxidation reaction provides a theoretical intrinsic volumetric and gravimetric capacity of 20.7 kAh/l and 4.1 kAh/kg and an intrinsic volumetric energy density of 32 kWh/l, which is higher than that of gasoline (∼10 kWh/l). Experimental discharge has yielded 3.7 kAh/kg to a 0.4 V discharge cutoff. 1 VB 2 corrodes at a slow rate in alkaline media, releasing hydrogen. However, we have demonstrated that a zirconia coating stabilizes VB 2 , when in contact with alkaline electrolytes, to minimize this self discharge reaction for alkaline batteries containing a VB 2 anode. 6,7 Traditionally, vanadium boride was prepared by high-temperature reaction of boron with metals, 8,9 or via carbothermal reduction of V 2 O 5 and B 2 O 3 above 1600 • C. 10 There have been a variety of other synthesis methods proposed for the formation of vanadium diboride, including a self-propagating high temperature synthesis from the elemental forms of vanadium and boron, 11 a nanocrystalline synthesis of VB 2 from the 650 • C solid state reaction VCl 4 , NaBH 4 and Mg, 12 as well as a mechanochemical procedure that utilized VCl 3 , LiH and LiBH 4 . 13 With the latter synthesis, VB 2 impurities prevent effective anodic discharge, but were sufficient to demonstrate that the nano-VB 2 yields higher open circuit potentials compar...

This study explores a new high temperature molten hydroxide domain to electrochemically split water into hydrogen fuel. Hydrogen fuel, if produced without greenhouse gas emissions, is a promising fuel for transportation. This study opens a pathway to low energy water splitting and the electrolytic production of hydrogen fuel without carbon dioxide emission. A wide range of pure and mixed alkali and alkali earth hydroxide electrolytes are explored at temperatures ranging from 200 to 700 • C. Higher temperature leads to improved (lower voltage) water splitting and improved rates of charge transfer, but carries challenges (increased rates of parasitic side reactions as the molten electrolytes dehydrate with increasing temperature). This study extends the range of hydrogen formation in alkaline electrolysis water splitting to over 600 • C, and demonstrates that lithium and/or barium hydroxide electrolytes remain hydrated at high temperatures, and in the high temperature domain are advantageous over sodium or potassium hydroxide electrolytes. In pure LiOH, the coulombic efficiency for hydrogen generation decreases with temperature and is measured respectively at η H 2 = 88%, 21%, 4% and 0%, respectively at 500, 600, 700 and 800 • Hydrogen has advantageous features compared to fossil fuels. It has a higher specific energy, is not polluting, has a combustion product of water, and in particular it does not emit the greenhouse gas carbon dioxide. Challenges of hydrogen storage are being addressed and hydrogen powered vehicles have been introduced to the commercial marketplace.1-4 Unfortunately, the predominant fraction of hydrogen generated today is produced by steam reformation of fossil fuel by reacting the fossil fuel with steam to release H 2 and CO 2 . Steam reformation is a substantial source of CO 2 emissions, negating the climate mitigation effect of using H 2 as a fuel. Thus, a process to efficiently generate hydrogen without carbon dioxide emissions is needed.The development of electrolytic splitting of water dates back to 1802. 5 The electrolysis of water produces hydrogen and oxygen directly without CO 2 emission (if the energy source used to generate the electricity did not release CO 2 ). Utilization of renewable or nuclear energy to generate the electricity for this electrolysis can drive this electrolytic water splitting to produce hydrogen as a fuel without carbon dioxide emissions. The most abundant of renewable energy resource for electrical generation is solar energy, and as early as 2001 we were driving stable solar electrolytic water splitting to hydrogen fuels at over 18% solar to chemical energy conversion by using efficient multiple bandgap solar cells.6 One of the challenges to the use of illuminated junctions to drive electrochemical or photoelectrochemical water splitting is that the bandgap of efficient semiconductors lies in the visible spectrum which generate a photo-potential less than the minimum needed rest potential of 1.23 volt required to split water to hydrogen and oxygen at room te...

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The electrochemical discharge of VB 2 is a unique process that involves the multiple electron per molecule oxidation of the tetravalent transition metal ion, V (+4 → +5), and each of the two borons 2×B (−2 → +3), corresponding to a net 11 electron discharge mechanism of the VB 2 /air cell as described by the overall cell reaction: VB 2 + 11/4O 2 → B 2 O 3 + 1 2 V 2 O 5 . However, in the presence of alkaline electrolytes, the discharge products include alkali salts associated with vanadaic and boric acid. In this study, we used FTIR, XRD, and coulombic efficiency measurements to probe the discharge products of high capacity cells and isolate KVO 3 as the principal vanadium discharge product. Additionally, we show that K 2 B 4 O 7 is the probable borate product. From FTIR analysis in KOH electrolyte, it is evident that the alkaline VB 2 /air discharge reaction is: VB 2 + 11/4O 2 + 2KOH → 1 2 K 2 B 4 O 7 + KVO 3 + H 2 O. XPS shows that the surface structure of nanoscopic VB 2 is very different from macroscopic VB 2 , which may contribute to the improved electrochemical properties of the nanoscopic material. The understanding of the discharge process and factors affecting performance contribute to furthering the development of extremely high capacity VB 2 /air batteries that utilize multi-electron processes. Metallic zinc has been used as an anode material in the majority of aqueous primary systems due to zinc metal's high two-electron oxidation capacity and effective discharge. The zinc-carbon battery, known as the Leclanché cell, was first introduced in the 19 th century as a low-cost solution for early energy storage needs. The zinc cell, which produced approximately 65 Wh kg −1 , was ideal only for low-rate discharges.1,2 Until the development of the zinc/alkaline/manganese dioxide battery and the zinc/air cell, there was little improvement in primary batteries. The alkaline Zn/MnO 2 cell has since dominated primary electrochemical storage, providing 145 Wh kg −1 . Although more expensive than the zinc-carbon battery, the alkaline cell improved performance by increasing energy densities and power capabilities. The zinc/air battery, using external O 2 as the battery active cathode reactant further improves the energy density of primary battery systems. It would be useful for electronic devices to have even higher energy storage densities than that available with zinc/air batteries.3 Most metal/air batteries to date have been unsuccessful in reaching the high-energy densities that are made possible by multi-electron oxidations, due to material passivation or chemical instabilities. 4 To provide high energy density cells, there has been an effort to develop high-capacity multi-electron per molecule charge storage processes.5-21 Vanadium diboride (VB 2 ) undergoes a multiple electron oxidation process, which to its completion involves an extraordinary 11 electron per molecule oxidation, including oxidation of the tetravalent transition metal ion, V(+4 → +5), and each of the two borons 2xB(−2 → +3). VB 2 has an intri...

fuels. [5][6][7] Lubomirsky and co-workers [ 16 ] have also probed the electrolysis of lithium molten carbonates to produce carbon monoxide, and Chen and co-workers [ 17 ] have also probed electrolysis of mixed lithium, potassium molten carbonates to carbon.We have previously delineated the solar, optical, and electronic components of STEP. [ 6,13 ] In this study, we focus on the electrolysis component for STEP fuel. Specifi cally, we present the fi rst molten electrolyte sustaining electrolytic co-production of both hydrogen and carbon products in a single cell. Solid carbon (as coal) is used as the starting point to generate CO and hydrogen for the Fischer-Tropsch generation of a variety of fuels, such as synthetic diesel. [ 18 ] However, that process is carbon dioxide emitting intensive. Here, hydrogen and graphitic carbon are produced without carbon dioxide emissions and instead produced from water and carbon dioxide.This communication recounts our successful attempt to simultaneously co-generate hydrogen and solid carbon fuels from a mixed hydroxide/carbonate electrolyte in a "single-pot" electrolytic synthesis at temperatures below 650 °C. The alternative co-generated hydrogen and gaseous carbon monoxide fuel synthesis will be pursued in a later study as the high temperature (over 900 °C) currently required to form CO in molten carbonates is a challenge to make compatible with the lower temperature range we have succeeded for hydrogen in the hydroxide electrolyses. We demonstrate here the functionality of new lithium-barium-calcium hydroxide carbonate electrolytes to co-generate hydrogen and carbon fuel in a single electrolysis chamber at high current densities of several hundreds of mA/cm 2 , at low electrolysis potentials, and from water and CO 2 starting points, which provides a signifi cant step towards the development of renewable fuels.Molten hydroxides are important as conductive, high-current, low-electrolysis-potential electrolytes for water splitting to generate hydrogen that have not been widely explored. [ 3,6,19,20 ] The pure anhydrous akali hydroxides melt only at temperatures >300 °C: LiOH ( T mp = 462 °C), NaOH ( T mp = 318 °C), KOH ( T mp = 406 °C), CsOH ( T mp = 339 °C). The mixed hydroxides have lower melting point. With molar ratios of 0.3:0.7 LiOH/NaOH, 0.3:0.7 LiOH/KOH, 0.5:0.5 NaOH/KOH, 0.44:0.56 KOH/CsOH, respectively, these melt at 215 °C, 225 °C, 170 °C, and 195°C, and the melting point is even lower when hydrated hydroxide salts are used. A eutectic 0.45:0.55 mix of LiOH/Ba(OH) 2 melts at 320 °C, compared to 407 °C for anhydrous Ba(OH) 2 , and 300 °C for the monohydrate Ba(OH) 2 ·H 2 O. [ 21 ] Low temperature enhances electrolytic H 2 formation in molten hydroxides. The coulombic effi ciency of electrolytic water splitting, η H2 (moles H 2 generated per 2 Faraday of applied charge),